PI3Ks are lipid kinases that function as signal transducers downstream of cell surface receptors and mediate pathways important for cell growth, proliferation, adhesion, survival and motility (1, 2). Although increased PI3K activity has been observed in many colorectal and other tumors (3, 4), no intragenic mutations of PI3K have been identified.
Members of the PIK3 pathway have been previously reported to be altered in cancers, for example, the PTEN tumor suppressor gene (15, 16), whose function is to reverse the phosphorylation mediated by PI3Ks (17, 18). Reduplication or amplification of the chromosomal regions containing PIK3CA and AKT2 has been reported in some human cancers (2, 19, 20), but the genes that are the targets of such large-scale genetic events have not been and cannot easily be defined.